<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>hello world</title>
</head>
<body>
    <h1 id="hw">hello world</h1>
    <button type="button" name="button" onclick="change()">点击</button>
</body>
<script type="text/javascript">
    var hw = document.getElementById("hw");
    function change(){
        hw.innerHTML = "change";
    }
    // btn

</script>
</html>
